Can I replace main run rigid pipe with hose?

No. The main run and branches must be rigid copper, properly fixed.
Hose may be run between a rigid pipe (fixed) and an appliance, BUT only if the appliance instructions allow it, and if it is a short as practicable, and if it accessible for inspection.
A hose can be run from the rigid pipe of the “vehicle” to the rigid pipe of a “slide out”.
Remember all hose locations needs to be stated in your handover manual (see Clause  5.2.5).